The present invention relates to a parenteral catheter apparatus
Injection devices which use a sharp needle to enter human tissue are now widely recognized as being hazardous to users and other individuals because the sharp point, contaminated by its exposure to the tissue of the first person may penetrate the skin of a second person and in doing so may carry micro-organisms from the patient on whom the injection device was first used into the tissue of a second person. Such transmission may result in the development of disease in the second person and when the puncture of the skin is accidental it is referred to as xe2x80x9cneedlestick injuryxe2x80x9d or xe2x80x9cneedleprick injuryxe2x80x9d.
Some clinical procedures require that a soft flexible tube, frequently called a catheter, is introduced into a tube or blood vessel such as a vein or artery or a parenteral fluid passage such as within the nervous system in the living body. This procedure is required, for example, to draw blood from a vein of a blood donor or from a patient for pathology testing; to infuse parenteral fluid nutrition or medication, especially when large volumes, for example several litres, are required to be infused over many hours; and also to enter the veins of patients who cannot be relied on to remain immobile during the procedure, in which situation a flexible catheter, rather than a stiff steel needle, greatly facilitates the procedure and is much less likely to damage the wall of the blood vessel.
The catheter is soft and flexible it cannot be used to penetrate the skin or the wall of the blood vessel and this is generally achieved by inserting a stiff sharp needle, which is generally called a trocar, through the lumen of the catheter so that the sharp tip of the trocar protrudes slightly during the procedure and pierces the tissue, splinting and carrying the catheter into the blood vessel. Having achieved this the operator then withdraws the trocar and discards it in a thick-walled container called a xe2x80x9csharps containerxe2x80x9d. During this procedure strict rules are followed in order to avoid needlestrick injury, with the risk of nosocomial disease transmission, but the risk is high. There are other disadvantages associated with this arrangement. Withdrawal of the trocar leaves the catheter or a container which may be attached to it, open, so that for example blood. can leak from a vein. To prevent this the operator quickly attaches a tube or syringe or other container to the open end of the container attached to the open catheter. Another disadvantage is that confirmation that a bodily fluid has been entered, by observation of flow of that fluid, called flashback, along the lumen of the catheter, can only be achieved by first removing the trocar.
If the catheter is in fact in the chosen location the trocar may have to be re-introduced and the tissue further penetrated, with consequent danger of the introduction of infective particles into the living body. Ingenious techniques have been devised in attempts to overcome these problems. There are several topological problems in achieving this. If The trocar is to be moved to a position within the device where there is no danger of contacting infectious agents or of causing a needlestick injury then some handle means must be provided which is accessible from outside the device but acts on the trocar within the device. This may be in the form of a thread which must pass through a wall of the device. To achieve observable flashback, a very fine tube or channel may be formed in the trocar, but because of the topological restraints this channel must be too fine to be useful in delivering or drawing out fluid and, like other trocars, must be removed from the fluid channel in order to bring the device into the useable state.
It is an object of the present invention to alleviate these problems at least in part.
In accordance with one aspect of the present invention there is provided a parenteral catheter apparatus characterised in that it comprises a thin walled catheter having a free end, the catheter closely enclosing a tubular needle having a sharp point, the catheter being mounted to a housing having a first end and a second end, the needle and catheter being longitudinally moveable relative to one another between a first position at which the needle extends from the catheter so that the sharp point is exposed and a second position at which the sharp point is within the catheter, the needle remaining in a fluid pathway of the parenteral catheter apparatus at all times between the first and second positions, the sharp point of the needle being arranged to pierce tissue when the catheter and the needle are in their relative first position, and the needle being connected or arranged to be connected to a tubular member arranged to be connected to a fluid container so that, in use, when the catheter and the needle are in their relative second position, parenteral fluid flows in order from the container into the tubular member, into the needle and into the catheter or fluid flows in the reverse direction in order into the catheter, into the needle, into the tubular member and then into the container.